Diazotype materials



United States Patent 3,464,823 DIAZOTYPE MATERIALS Bernard I. Halperin, Glen Aubrey, N.Y., and James 0. Thompson, Los Gatos, Calif., assignors to International Business Machines Corporation, Armonk, N.Y., a corporation of New York No Drawing. Filed Dec. 28, 1965, Ser. No. 517,092 Int. Cl. G03c 1/60, N54 US. Cl. 96-49 4 Claims ABSTRACT OF THE DISCLOSURE A method for producing diazotype images comprising image-wise exposing a light-sensitive diazonium salt and and a lignin material containing a member from the group consisting of a coniferyl aldehyde derivative of lignin and a syringaldehyde derivative of lignin and developing in an alkaline medium to produce an azo dye image.

A diazo type material comprising a substrate having a light sensitive coating comprising a light sensitive layer comprising a light sensitive diazonium salt and a lignin material containing a member selected from the group consisting of a coniferyl aldehyde derivative of lignin and a syringaldehyde derivative of lignin.

The present invention relates to new diazotype materials and in particular to diazotype materials in which lignin and lignin derivatives are present as couplers.

In general, diazotype materials comprise a light-sensitive diazonium salt and a coupler which is capable of reacting with the salt to produce an image. The lightsensitive diazonium salt and coupler may be combined in a variety of ways, but two general approaches to diazotype image formation are generally employed. First, the light-sensitive diazonium salt and coupler are combined and applied as a coating or impregnant to a substrate, such as a sheet of paper, film or the like. Suitable stabilizing materials such as acids are incorporated in the formulation to prevent premature coupling. The elements are then selectively exposed to light and developed by the application of an alkaline developing fluid in the form of a gas or a liquid. Alternatively, the light-sensitive diazonium salt alone may be deposited in or on a substrate, exposed and then developed by the application of a coupler usually applied together with an alkaline developing fluid.

While the present invention has application in both general types of diazotype systems, its primary advantage is realized in the former method of application known as a two component system.

The primary object of the present invention is to provide new highly economical, diazotype materials well suited to the production of high quality diazotype images.

In accordance with the present invention, highly useful diazotype materials are provided by first preparing a paper substrate ordinarily in the form of a flexible sheet of paper, containing a substantial amount of lignin or derivative of lignin such as coniferyl aldehyde and syringaldehyde. The paper substrate is then coated or impregnated with a solution containing a light-sensitive diazonium salt which is deposited in or on the substrate reactively associated with the lignin material. It has been found that the lignin naturally occurring in papers formed from woody materials is a very satisfactory coupler for light-sensitive diazonium salts and provides the basis for producing a very economical, two component diazotype paper.

While this is the most inexpensive form for producing papers according tothe invention, it will be understood that additional amounts of lignin may be added to a 3,464,823 Patented Sept. 2, 1969 paper not containing lignin or containing insufficient amounts to provide the desired color formation upon exposure and development. In general, a content of lignin or lignin derivative of 5 to 10% by weight or more of the paper is sufiicient to provide a suitable source of coupler for producing good diazotype images.

Where the lignin is separately added to the paper or the lignin content of the paper is supplemented by such an addition, this may be done on machine, that is, during the paper forming operation or off machine that is, at a stage subsequent to paper formation. The latter would include for example, coating, sizing or impregnating the paper with a lignin containing solution.

The chemical composition of lignin is not known with precision. Lignin is the major non-carbohydrate constituent of wood and woody plants and may comprise about 25% of such materials. It functions as a natural plastic binder for the cellulosic fibers of wood, straw, etc. Rather than referring to a specific compound, the term lignin actually is a collective term for a group or system of compounds of high molecular weight. A summary of the functional groups and interunit linkages in lignin, as it is now unknown, is described by E. Adler in Das Papier, 15, page 604 (1961). The color forming group is generally regarded to be the coniferyl aldehyde group.

Paper containing lignin may be readily produced by controlling the pulping action during the paper making process. During the manufacture of paper pulp from wood (there is no lignin in cotton), straw, etc., by the conventional chemical processes, such as sulfate (kraft), sulfite and soda pulping, a certain amount of the hemicelluloses and lignin are removed. In the less expensive types of paper produced by the milder chemical processes commonly referred to as semi-chemical or chemi-ground wood, a very large percentage of the lignin originally present in the original fiber (wood, straw, etc.) is retained in the pulp.

As an example, suitable papers were prepared from the following pulps on the web former of the Institute of Paper Chemistry:

(1) Hardwood unbleached sulfite (Magnifite process);

(2) Softwood unbleached sulfite (Mitscherlich process);

(3) Hardwood neutral sulfite semi-chemical;

(4) Hardwood chemi-groundwood, and

(5) Softwood groundwood from chips given a mild sulfite-bisulfite pretreatment.

Especially in newsprint or ground wood papers, almost all of the lignin in the original wood is present unchanged in the final paper. Such low cost papers containing significant amounts of lignin are particularly useful in the present invention. However, it should be understood that other paper materials may also be used and that the lignin may be separately introduced or impregnated into the paper during or after its formation. This, of course, is a much less efficient method for producing the lignin containing paper sheet than by conducting a pulping operation which results in a paper containing a substantial or effective amount of lignin. v

Conventional light-sensitive diazonium salts may be employed to couple with lignin to produce useful images. Representative compounds include, for example p-diazodiphenylamine sulfate, p-diazo-diethylaniline-zinc chloride, p-diazo-dimethylaniline borofiuoride, p diazo 1- morpholinobenzene- /2 Zinc chloride, p-diazo-N-diethyl- M-phenetidine borofiuoride, etc.

While the invention has been described in terms of a preferred embodiment, certain alternate embodiments are also contemplated. For example, the lignin and a lightsensitive diazonium salt may be jointly or separately added to a substrate initially not containing an effective amount of lignin. This addition may be made by incorporating the lignin and light-sensitive diazonium salt in the body of the substrate or by coating the materials as a composition on the surface of the substrate. Also, the lignin may be incorporated into the developing solution which is brought into contact with a substrate containing or coated with a light-sensitive diazonium salt. Conversely, the lignin might be selectively impregnated into or coated on the surface of a substrate and then contacted with a lightsensitive diazonium salt and developed to produce images where the lignin is present.

In general, therefore, the present invention encompasses diazotype materials which initially or ultimately comprise a light-sensitive diazonium salt reactively associated with lignin so that under the proper circumstances and in the proper developing environment, the reaction between the salt and lignin may proceed to provide useful diazotype images.

As an example of the present invention a hardwood neutral sulfite semichemical pulp is formed into a thin paper sheet which is calendered and dried. The sheet is then coated with a solution of 1.5% by weight 2,5- diethoxy-p morpholinobenzenediazoniumfluoborate and 10% citric acid in a solvent composed of 30 volumes of methylethyl ketone and 40 volumes of methylcellosolve. The solution was dried to deposit a film of the light sensitive diazo salt and stabilizing acid on the surface of the paper. The resulting copy sheet was then selectively exposed and the image developed in a standard Ozamatic developer which utilizes an aqueous ammonia developing fluid.

It will be obvious to those skilled in the art that various modifications may be made in the process and materials described herein without departing from the spirit and scope of the invention as expressed in the following claims.

What is claimed is:

1. A diazo type material comprising a substrate having a light sensitive layer comprising a light sensitive diazonium salt and a lignin material containing a member from the group consisting of a coniferyl aldehyde derivative of lignin and a syringaldehyde derivative of lignin.

2. A method for producing diazotype images comprising image-wise exposing the diazotype material described in claim 1, and developing said material in an alkaline medium to produce an azo dye image.

3. The diazotype material of claim 1 wherein a portion of said lignin material is separately added to said paper during the paper formation.

4. The diazotype material of claim 1 wherein a portion of said lignin material is coated on the surface of said substrate, and said light-sensitive diazonium salt is also coated on the surface of said substrate.

References Cited UNITED STATES PATENTS 2,245,628 6/1941 Von Poser et al. 96-91 2,694,010 11/1954 Botkin et a1. 96--75 2,726,956 12/1955 Jahoda 96-75 OTHER REFERENCES Casey, James P.: Pulp and Paper, 2nd ed., vol. II, Interscience Pub. Ltd., London, TS1105SC29 1960, pp. 52-64.

Casey, James P.: Pulp and Paper, 2nd ed. vol. II, Interscience Pub. Ltd., London, TS1105SC29 1960, pp. 704-705.

Grant, Julius: Hackhs Chemical Dictionary, 3rd ed., 1944, McGraw-Hill Book Co., N.Y., pp. 221, 338, 491 and 826.

Chem. Abstracts (I), vol. 60, p. 9240c, April 1964; Chem. Abstracts (II), vol. 60, p. 922lh, April 1964; Chem. Abstracts (III), vol. 63, p. 7826-e, July 1965; Chem. Ab. (TV), vol. 63, p. 11851e-h, October 1965; Chem. Ab. (V), vol. 64, p. 3825e-g, January 1966; Chem. Ab. (VI), vol. 43, p. 4461g-h, June 1949; Chem. Ab. (VII), vol. 44, p. 1258e-f, April 1950; Chem. Ab. (VIII), vol. 44, p. 8637e-i, November 1950; Chem. Ab. (IX), vol. 52, p. 11413hi; Chem. Ab. (X), vol. 53, p. 4445bc, March 1959.

NORMAN G. TORCHIN, Primary Examiner C. BOWERS, Assistant Examiner US. Cl. X.R. 96-75, 91 

